Plasticity of Electrical Synapses

描述(由申请人提供)：本提案的目的是研究缝隙连接介导的电突触在听觉系统中的作用和特性。终止为金鱼Mauthner细胞上大型(电和化学)混合突触终末的听觉传入非常适合于这些研究，因为与哺乳动物的电突触不同，实验的可及性使人们能够量化在不同生理条件下发生的体内连接电导的变化，并将它们与解剖学、超微结构和分子分析相关联。值得注意的是，这些模型电突触的电导受到神经元活动的精细调控。电传递是由连接蛋白35(Cx35)介导的，连接蛋白35(Cx35)是哺乳动物连接蛋白36(Cx36)的同源基因，存在于听觉系统中，这表明哺乳动物的听觉电突触也可能受到类似的调控。这项建议涉及通过集中于间隙连接通道的调节运输的作用来理解这些末端连接电导的双向控制的分子机制。目的1结合超微结构和药理学方法，在活体内研究缝隙连接通道在天然电突触上运输的存在。我们的初步结果表明，缝隙连接通道存在活跃的翻转，这是在自然突触中这一现象的第一个证据。目的2是确定受调控的贩运对电传递的活性依赖增强的贡献。它将测试增强的表达是否需要胞吐机制，以及是否需要与调节激酶CaM-KII和支架蛋白ZO-1直接相互作用。相反，目标3将调查受管制的贩运对依赖活动的电力传输抑制的可能贡献。使用类似的方法，我们将调查是否需要内吞机制来依赖活性抑制连接电导，以及直接蛋白质-蛋白质相互作用的潜在作用。此外，CaM-KII和ZO-1通过Cx35和Cx36的保守区的直接相互作用表明，它的功能可能是电传递的基本和广泛特性的基础，也与哺乳动物的电突触有关。因此，这项研究提出了一个新的概念，即电突触的强度是通过动态调节缝隙连接通道的运输来实现的。由于电突触已被证明能促进神经元的协调活动，这一调节的功能障碍可能会产生深远的病理影响，导致听觉障碍、癫痫、认知(精神)和发育障碍。 与公共健康相关：该提案探索了缝隙连接介导的电子突触调控的分子机制。此外，该提案还探讨了受管制的缝隙连接通道贩运作为其基本机制的作用。这一过程已被证明参与了化学突触的调节，但没有证据表明它参与了电突触。因此，该提案调查了化学突触和电突触共享共同调控机制的可能性。由于电突触已被证明可以促进神经元的协调活动，它们的调节功能障碍可能会产生深远的病理影响，导致癫痫以及认知(精神)和发育障碍。

DESCRIPTION (provided by applicant): The goal of this proposal is to investigate the role and properties of gap junction-mediated electrical synapses in the auditory system. Auditory afferents terminating as large mixed (electrical and chemical) synaptic terminals on the goldfish Mauthner cell are ideally suited for these studies since unlike mammalian electrical synapses, the experimental accessibility makes it possible to quantify in vivo changes in junctional conductance that occur under different physiological conditions and to correlate them with anatomical, ultrastructural and molecular analysis. Strikingly, the conductance of these model electrical synapses is under the fine regulatory control of neuronal activity. Electrical transmission is mediated by connexin 35 (Cx35), the fish ortholog of the mammalian connexin 36 (Cx36) which is present in the auditory system, suggesting that mammalian auditory electrical synapses could be similarly regulated. This proposal deals on understanding the molecular mechanisms underlying the bi-directional control of junctional conductance at these terminals by focusing in the role of regulated trafficking of gap junction channels. Aim 1 is to investigate the existence of trafficking of gap junction channels at native electrical synapses, in vivo, by combining ultrastructural and pharmacological approaches. Our preliminary results suggest the existence of an active turnover of gap junction channels, which constitute the first evidence of this phenomenon in a native synapse. Aim 2 is to determine the contribution of regulated trafficking to activity-dependent potentiation of electrical transmission. It will test if mechanisms of exocytosis are required for the expression of the potentiation and if it requires of direct interactions with the regulatory kinase CaM-KII and the scaffold protein ZO-1. Conversely, Aim 3 will investigate the possible contribution of regulated trafficking to activity-dependent depression of electrical transmission. Using similar approaches, we will investigate if mechanisms of endocytosis are required for activity-dependent depression of junctional conductance, as well the potential roles of direct protein-protein interactions. Furthermore, the direct interactions of CaM-KII and ZO-1 through conserved regions of both Cx35 and Cx36 suggests that its function might underlie a fundamental and widespread property of electrical transmission, also relevant to mammalian electrical synapses. Thus, the proposed research addresses the novel concept that the strength of electrical synapses is achieved by dynamically regulating the trafficking of gap junction channels. Because electrical synapses have been shown to promote coordinated neuronal activity, dysfunction of this regulation could have profound pathological implications, contributing to auditory impairment, epilepsy and cognitive (psychiatric) and developmental disorders PUBLIC HEALTH RELEVANCE: The proposal explores the molecular mechanisms involved in the regulation of gap junction-mediated electrical synapses. Further, the proposal explores the role of regulated trafficking of gap junction channels as their underlying mechanism. This process has been shown involved in the regulation of chemical synapses, but no evidence suggests its participation in electrical synapses. Thus, the proposal investigates the possibility that both chemical and electrical synapses share common regulatory mechanisms. Because electrical synapses have been shown to promote coordinated neuronal activity, dysfunction of their regulation could have profound pathological implications, contributing to epilepsy and to cognitive (psychiatric) and developmental disorders.